Hello,
1.It is called as pica that is craving for unusual things like chalk, mud,raw food etc which is presumed to occur due to deficiency of nutrition, especially calcium.
2. Delayed menses could be due to various reason like pregnancy, hormonal dysfunction, stress etc.
It is important to discuss other questions related to your health to come to final diagnosis behind delayed menses and the craving.
You can discuss in detail with me, by having a online consult fix.

Hello lybrate-user,
Scanty periods can occur due to thyroid disorders or Pcos or Hormonal Imbalance or Nutritional deficiency or Stress. Homeopathy offers safe, gentle cure for regularising menses with in less period of time and without side effects like weight gain or excessive hairgrowth.

Yes after 15 days of the monthly period she can be pregnant as it's the unsafe days and unprotected intercourse can leads to pregnancy. For confirmation go for urinary pregnancy test using prega news kit.

After 2 to 3 days of delivery there is yellowish milk which is also called as colostrum and it is good for your baby. And its not for husband. Yellow colour milk or colostrum prevents your baby from diseases.